Block-copolymers with highly sulfonated ionomer blocks are considered as leading candidates for low-humidity high-temperature Polymer Electrolyte Fuel Cell membranes. We present a new approach that allows for faster measurement of conductivity of powdered ionomers in a wide range of temperature and humidity with a single 10-30 mg sample. Our method is exemplified by a case study of polyphenylenesufide with a degree of sulfonation 0.70. This material shows 0.12 S/cm conductivity at 127 A degrees C and 50% relative humidity. At higher temperatures and lower humidities, this polymer undergoes irreversible cross-linking. Further routes to improving conductivity, chemical and mechanical properties of the polymer are discussed.